chown -c -R Useful in changing the ownership of an assigned or owned file. touch -a -t Useful in creating or modifying a file timestamp. chmod -c -R Assign a file the read, write, and execute permissions. chown The ownership of the file called file_name is assigned or changed to a new owner called user. chmod 766 The owner of the file called file_name has complete access to it while group and other users can only read and execute. chmod 755 The owner of the file called file_name will have read, write, and execute permissions while other users will only have read and execute permissions. chmod 777 Everyone access the file called file_name will have read, write, and execute permissions. chown user:group file_name The user and group privileges linked to file_name are changed. chown root /u In this command, the ownership of /u is transferred to the root user. Command Description ls -l Outputs the file type and the file permissions needed to access the target file. Use the table below to set file permissions in Linux. file_one: This is the name of the file. In this case, the file was last modified on February 20th at 15:11. Feb 20 15:11: This is the file’s last modification date and time.You can verify that by downloading the acl package, then running the "getfacl /dev/snd/* " terminal command, it should list the current logged in user as having read and write access. It does so by setting access rights to the sound device nodes (i e everything under /dev/snd/* ). The ConsoleKit daemon automatically switches access to the audio device according to the currently logged in user. The risk involved here is that if a malicious or badly written program makes use of these privileges, it can cause the entire system to lock up, or at least become very sluggish. This can be necessary for running low-latency audio without drop-outs. In recent versions of Ubuntu, when installing the Jack daemon, it optionally installs a file giving every user in the audio group real-time privileges, and possibilities to prevent program memory from being swapped. A can also record from the sound cards inputs, so if the machine e g has a built-in microphone, A could in a sense "spy" on B. Should A decide to do so, this means that B suddenly cannot play audio anymore while A is using it. A, who is in the audio group, logs in remotely, and can now grab access to the sound card. Or assume that B is sitting in front of the computer, not using the sound card at the moment. Since A can still use the sound card, A's music will continue to play and user B can't access the sound card (regardless of whether B is in the audio group or not). User B wants the computer temporarily, so they switch users (via fast-user-switching, without user A logging out). So assume, for example, that user A is in the audio group is logged in, and is playing music. And at the lowest level, only one user/application can grab access to the sound card at the same time. If you decide you want the user to be in the Audio group, you should know that this user can access the sound card even if he is not logged in. This command should not lists any normal user, in fact, everything except "pulse" (which is reserved for system-wide usage of PulseAudio, and is normally not used) is a cause for concern. Open a terminal and run this command: fgrep -ie 'audio' /etc/group
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